Atherosclerotic cardiovascular disease is common, and is caused by a narrowing of the arterial lining due to atherosclerotic plaques. When plaque builds up, this is referred to in the art as stenosis. One method commonly employed to relieve arterial stenosis resulting from plaque build-up is percutaneous transluminal coronary angioplasty, or balloon angioplasty. PTCA or balloon angioplasty, is a non-invasive, non-surgical means of treating coronary arteries.
This technique consists of inserting a non-inflated balloon catheter into the affected artery. Dilation of the diseased segment of artery is accomplished by inflating the balloon which pushes the atherosclerotic lesion outward, compressing the stenosis and enlarging the arterial diameter.
To effectively expand the lumen and compress the stenosis, it is desirable that the balloon be reliably inflatable to a predetermined diameter when the balloon is infused with fluid. This is so in order to evenly expand the balloon within the affected artery to evenly dilate the vessel, compress and hence compromise the stenosis. Also, it is desirable that the balloon be reliably collapsible to a minimal, radially compact cross sectional shape incident to balloon insertion and withdrawal. This is to facilitate insertion and withdrawal of the balloon in artery. While existing angioplasty balloons are collapsible, they may not always be reliably so, and may flatten into a “pancake” like shape, rather than to a radially compact minimal cross-section, particularly after inflation to a relatively large diameter.
This flattening can increase the possibility that the balloon may interfere with the arterial wall during balloon withdrawal or when being placed across a second stenosis. This pancake-like balloon shape can increase the difficulty of withdrawal after inflation.
Various techniques or balloon constructions have been employed to facilitate the folding of the balloon about the balloon catheter in a uniform manner upon evacuation and deflation of the balloon after use.
One method employed to improve the refoldability of the balloon and improve withdrawal, has been to fold the balloon to form a number of wings. Prior to use, the balloon is typically folded or wrapped about the balloon catheter to fit within and pass through the guide catheter lumen. When inflation fluid is applied to the deflated balloon, the balloon wings or flaps unwrap and the balloon inflates to a fully expanded condition. After inflation, and in the deflated state, the balloon collapses upon itself forming flaps or wings that must be folded or wrapped around the balloon catheter to allow it to be withdrawn from the patient's vasculature after use.
A number of approaches have been employed in forming a balloon that will refold into wings or flaps about the catheter shaft.
One approach has been to construct the balloon of a cylinder of material, such as polyethylene, that is uniform about its circumference but can be heat set after it is wrapped or folded to form curved, overlapping flaps or wings extending from fold lines in a manner described further below. Heat setting of the balloon results in a balloon that when, upon application of negative pressure during deflation, will return fairly closely to its tightly wrapped heat set configuration.
Another approach has been taken to fabricate the balloon itself with fold line structures and flap shapes, particularly for use with balloons formed of stronger polyesters, for example, polyethylene terepthalate (PET).
See, for example, U.S. Pat. Nos. 5,226,887, 5,318,587, 5,456,666 and 5,478,319 for various methods of improving balloon collapsibility after inflation. The entire content of these patents is hereby incorporated by reference herein.
There remains a need, however, for innovative and improved methods for folding balloons and for improved balloon refold.
The art referred to and/or described above is not intended to constitute an admission that any patent, publication or other information referred to herein is “prior art” with respect to this invention. In addition, this section should not be construed to mean that a search has been made or that no other pertinent information as defined in 37 C.F.R. §1.56(a) exists.
All US patents and applications and all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.
Without limiting the scope of the invention a brief summary of the claimed embodiments of the invention is set forth below. Additional details of the summarized embodiments of the invention and/or additional embodiments of the invention may be found in the Detailed Description of the Invention below.